Add ThemeAssetsReader which reads assets from a theme

If the theme includes the 'assets' directory, it will be walked and items will be added to the site based
on the normal rules of Jekyll: if there is YAML front matter, it will be added as a (convertible) Page,
otherwise it will be added as a StaticFile.

lib/jekyll.rb

@@ -55,6 +55,7 @@ module Jekyll
   autoload :PostReader,          "jekyll/readers/post_reader"
   autoload :PageReader,          "jekyll/readers/page_reader"
   autoload :StaticFileReader,    "jekyll/readers/static_file_reader"
+  autoload :ThemeAssetsReader,   "jekyll/readers/theme_assets_reader"
   autoload :LogAdapter,          "jekyll/log_adapter"
   autoload :Page,                "jekyll/page"
   autoload :PluginManager,       "jekyll/plugin_manager"

lib/jekyll/page.rb

@@ -40,7 +40,11 @@ module Jekyll
       @base = base
       @dir  = dir
       @name = name
-      @path = site.in_source_dir(base, dir, name)
+      if site.in_theme_dir(base) == base # we're in a theme
+        @path = site.in_theme_dir(base, dir, name)
+      else
+        @path = site.in_source_dir(base, dir, name)
+      end
 
       process(name)
       read_yaml(File.join(base, dir), name)

lib/jekyll/reader.rb

@@ -18,6 +18,7 @@ module Jekyll
       sort_files!
       @site.data = DataReader.new(site).read(site.config["data_dir"])
       CollectionReader.new(site).read
+      ThemeAssetsReader.new(site).read
     end
 
     # Sorts posts, pages, and static files.

lib/jekyll/readers/theme_assets_reader.rb

@@ -0,0 +1,31 @@
+module Jekyll
+  class ThemeAssetsReader
+    attr_reader :site
+    def initialize(site)
+      @site = site
+    end
+
+    def read
+      return unless site.theme && site.theme.assets_path
+
+      Find.find(site.theme.assets_path) do |path|
+        next if File.directory?(path)
+        if File.symlink?(path)
+          Jekyll.logger.warn "Theme reader:", "Ignored symlinked asset: #{path}"
+        else
+          base = site.theme.root
+          dir = File.dirname(path.sub("#{site.theme.root}/", ""))
+          name = File.basename(path)
+          relative_path = File.join(*[dir, name].compact)
+          if Utils.has_yaml_header?(path)
+            next if site.pages.any? { |file| file.relative_path == relative_path }
+            site.pages << Jekyll::Page.new(site, base, dir, name)
+          else
+            next if site.static_files.any? { |file| file.relative_path == relative_path }
+            site.static_files << Jekyll::StaticFile.new(site, base, dir, name)
+          end
+        end
+      end
+    end
+  end
+end

lib/jekyll/theme.rb

@@ -18,15 +18,19 @@ module Jekyll
     end
 
     def includes_path
-      path_for :includes
+      path_for :_includes
     end
 
     def layouts_path
-      path_for :layouts
+      path_for :_layouts
     end
 
     def sass_path
-      path_for :sass
+      path_for :_sass
+    end
+
+    def assets_path
+      path_for :assets
     end
 
     def configure_sass
@@ -43,7 +47,7 @@ module Jekyll
     end
 
     def realpath_for(folder)
-      File.realpath(Jekyll.sanitized_path(root, "_#{folder}"))
+      File.realpath(Jekyll.sanitized_path(root, folder.to_s))
     rescue Errno::ENOENT, Errno::EACCES, Errno::ELOOP
       nil
     end